[Development of a selective differential medium for the isolation of Corynebacterium urealyticum (group D-2)].

BACKGROUND

We have developed a new selective culture medium for the isolation of C. urealyticum, with the aim of improving and making easier the isolation and identification of this microorganism.

MATERIAL AND METHODS

The medium is based on components similar to other media, usually used for diagnosis of urinary tract infections, also containing glucose, urea, phenol red, polysorbate 80 (Tween 80), polymixin B, amphotericin B, nalidixic acid and lyncomycin. The medium was tested in 65 clinical isolates and three type strains, and in 533 clinical samples of urine.

RESULTS

All 65 clinical strains and 3 reference strains of C. urealyticum tested grew faster on this medium than on blood agar. E. coli, Klebsiella spp., Enterobacter spp., Citrobacter spp., M. morganii, Proteus spp., S. aureus, Enterococcus spp. and Corynebacterium spp. did not grow in the selective agar. S. epidermidis and Streptococcus spp. grew in less than 10% of cases, P. aeruginosa in 29.2% and Serratia spp. in 41.7%. The colonies were always easily differentiated from C. urealyticum. In the studies performed on 553 clinical samples from patients with urinary tract infections, six infections by C. urealyticum were detected. The growth of all strains being faster on this medium than on blood-agar.

CONCLUSIONS

This new selective medium may be a valuable tool for diagnosis of UTIs caused by C. urealyticum in patients with retard risk factors.